1. Field of the Invention
The present invention relates to an opto-electric hybrid module including an optical waveguide section, an electric circuit section, and an optical element mounted on the electric circuit section, and to a method of manufacturing the same.
2. Description of the Related Art
As shown in FIG. 8, an opto-electric hybrid module is constructed, for example, using a technique to be described below. First, an electric circuit section E1 in which an electric circuit 14 is formed on the surface of a substrate 15, and an optical waveguide section W1 in which an under cladding layer 11, a core 12 and an over cladding layer 13 are disposed in the order named are produced individually. The back surface of the substrate 15 in the electric circuit section E1 is bonded to the front surface of the over cladding layer 13 in the optical waveguide section W1 with an adhesive 16. A light-emitting element 7 and a light-receiving element 8 are mounted on portions of the electric circuit section E1 corresponding to opposite end portions of the core 12 in the optical waveguide section W1. Such a technique is disclosed, for example, in Japanese Patent Application Laid-Open No. 2004-302345. The substrate 15 includes light-passing through holes 15a and 15b formed therein for propagation of light L between the end portions of the core 12 and the light-emitting and light-receiving elements 7 and 8. A notch 19 of an inverted V shape is formed in the optical waveguide section W1 near each of the opposite ends of the core 12. One side surface defined by the inverted V-shaped notch 19 on the core 12 side is formed as an inclined surface inclined at 45 degrees to the axial direction of the core 12. An end portion of the core 12 lying at the inclined surface serves as a light reflecting surface 12a. In FIG. 8, the reference character 7a designates a light-emitting section in the light-emitting element 7, and 7b and 7c designate bumps in the light-emitting element 7. The reference character 8a designates a light-receiving section in the light-receiving element 8, and 8b and 8c designate bumps in the light-receiving element 8.
The propagation of the light L in the opto-electric hybrid module will be described. First, the light L is emitted downwardly from the light-emitting section 7a of the light-emitting element 7. The light L passes through the through hole 15a for light propagation formed in the electric circuit section E1 and then through the over cladding layer 13 near a first end portion (as seen in FIG. 8, the left-hand end portion) of the optical waveguide section W1, and thereafter enters a first end portion of the core 12. Subsequently, the light L is reflected from one of the light reflecting surfaces 12a provided in the first end portion of the core 12, and travels through the interior of the core 12 in the axial direction. The light L is propagated to a second end portion (as seen in FIG. 8, the right-hand end portion) of the core 12. Subsequently, the light L is reflected upwardly from the other light reflecting surface 12a provided in the second end portion of the core 12. Then, the light L passes through and exits from the over cladding layer 13, and is received by the light-receiving section 8a of the light-receiving element 8.
In the course of the above-mentioned propagation of the light L, the light L emitted from the light-emitting section 7a of the light-emitting element 7 is diffused as shown in FIG. 8. For this reason, if there is a long distance between the light-emitting element 7 and the light reflecting surface 12a provided in the first end portion of the core 12, the light L deviates away from the light reflecting surface 12a and is not guided into the core 12 in some cases. Similarly, the light L reflected from the light reflecting surface 12a provided in the second end portion of the core 12 is also diffused. For this reason, the light L deviates away from the light-receiving section 8a of the light-receiving element 8 and is not received by the light-receiving section 8a in some cases. It is therefore necessary to design the opto-electric hybrid module so as to minimize the distance between optical elements such as the light-emitting and light-receiving elements 7 and 8 and the light reflecting surfaces 12a provided in the end portions of the core 12 in the optical waveguide section W1.
Conventional opto-electric hybrid modules, however, are constructed such that the electric circuit section E1 comprised of the substrate 15 and the electric circuit 14 is disposed between the optical elements such as the light-emitting and light-receiving elements 7 and 8 and the optical waveguide section W1. This makes the distance between the optical elements such as the light-emitting and light-receiving elements 7 and 8 and the end portions of the core 12 accordingly long which thereby result in the lowered efficiency of light coupling therebetween.